<!DOCTYPE html>
<script src="../../../resources/run-after-layout-and-paint.js"></script>
If the red outline at the bottom of the div extends all the way to the scrollbar, the test passes.  If it stops short, then the test has failed, and an incomplete repaint has occurred.
<div id="t" style="overflow-y: scroll; outline: none; width: 80px; height: 69px;">
    <br><br><br><br><br><br><br><br><br><span id="z" style="outline: 3px solid red;">Failed Test</span>
</div>
<script>
document.getElementById("t").scrollTop = 91;
runAfterLayoutAndPaint(() => {
  document.getElementById("z").lastChild.data='Excellent! Test';
}, true);
</script>
